Headphone volume control method and headphone

ABSTRACT

A headphone volume control method calculates a level of a sound signal, which is captured by a microphone, during a first period, determines a target value of a sound volume based on the above-mentioned level, and gradually changes a reproduction volume of content to be reproduced to the above-mentioned target value over a second period.

CROSS REFERENCE TO RELATED APPLICATIONS

This Nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2019-234523 filed in Japan on Dec. 25, 2019the entire contents of which are hereby incorporated by reference.

BACKGROUND 1. Technical Field

One embodiment of the present disclosure relates to a headphone volumecontrol method that controls a volume of a headphone, and a headphone.

2. Background Information

U.S. Pat. Nos. 9,609,449 and 7,983,426 disclose a method for controllinga sound volume such that a total level of an environmental soundcaptured by a microphone and an output sound does not exceed athreshold.

SUMMARY

When using a headphone, a user may increase a sound volume of contentdepending on a volume of ambient environmental sounds. After that, evenif the surroundings become quiet, a user may continue to hear thecontent at a large volume, because the user gets used to a loud sound orfeels troublesome in a volume operation. The continuous hearing at alarge volume is not desirable from the viewpoint of hearing protection.However, if a sound volume of content is changed depending on a volumeof environmental sounds like U.S. Pat. Nos. 9,609,449 and 7,983,426, auser may notice the volume change and feel sense of incongruity.

An object of one embodiment of the present disclosure is to provide aheadphone volume control method capable of changing a sound volumewithout causing a user to notice the volume change, and a headphone.

The headphone volume control method calculates a level of a soundsignal, which is captured by a microphone, during a first period,determines a target value of a sound volume based on the above-mentionedlevel, and gradually changes a reproduction volume of content to bereproduced to the above-mentioned target value over a second period.

According to one embodiment of the present disclosure, a sound volumecan be changed without causing a user noticing the volume change.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a headphone 1.

FIG. 2 is a functional block diagram of the headphone 1.

FIG. 3 is a flowchart showing an operation of a processor 12.

FIG. 4 is a block diagram showing a functional configuration of aheadphone 12 in accordance with a modification.

DETAILED DESCRIPTION

FIG. 1 is a block diagram showing a configuration of a headphone 1. Theheadphone 1 includes a communication portion 11, a processor 12, a RAM13, a flash memory 14, a microphone 15, a speaker unit 16, and a userI/F 17.

The communication portion 11 receives a sound signal from an informationprocessing terminal such as a smartphone, or a player such as portablemusic playback equipment through wireless communications such asBluetooth (registered trademark). The present disclosure, however, isnot limited to a headphone for wireless communications. Thecommunication portion 11 may receive a sound signal from a playerthrough a communication cable or an audio cable. Further, the headphoneis not limited to an in-ear type of headphone that is inserted into anexternal auditory canal for use. The headphone may include an overheadtype of headphone having a head band.

Note that, FIG. 1 shows one of two units each being inserted into a leftear or a right ear for use. The two units have the same configurationand function. However, it is not necessary for the two units to have thesame configuration and function. For instance, either one of the twounits, i.e., a left ear unit or a right ear unit may include theconfiguration shown in FIG. 1 and control a volume of the sound signalto be supplied to the other unit. In this case, the other unit receivesthe sound signal, which is subjected to the volume control in the oneunit, and the sound signal is outputted from a speaker unit.

In FIG. 1, the processor 12 is constituted by a CPU, a DSP, an SoC(System on a Chip), or the like. The processor 12 reads out a programfrom the flash memory 14, serving as a storage medium, and stores it ina RAM 13 temporarily, thereby executing various kinds of operations. Theprogram includes a volume control program 141.

The flash memory 14 stores an operation program of the processor 12. Forinstance, the flash memory 14 stores the above-mentioned volume controlprogram 141. By executing the volume control program 141, the processor12 achieves a headphone volume control method and a headphone volumecontroller of the present disclosure.

The microphone 15 captures an ambient sound as a sound signal. Theambient sound contains an environmental sound. Note that, theenvironmental sound contains sounds other than content, for example, anoise. The microphone 15 converts the captured sound signal into adigital signal. The microphone 15 outputs the sound signal, which issubjected to the digital conversion, to the processor 12.

The processor 12 receives the sound signal in accordance with theenvironmental sound from the microphone 15. The processor 12 receives asound signal of content from the communication portion 11. The processor12 controls a volume of the sound signal of content based on a volumechange operation (a gain specifying operation) received from a user I/F17 and the sound signal received from the microphone 15. The processor12 outputs the sound signal of content to the speaker unit 16.

The speaker unit 16 converts the sound signal of content into an analogsignal. Based on the analog signal, the speaker unit 16 emits sounds.

The user I/F 17 receives an operation from a user. The operationreceived from a user includes volume change (gain specification), forexample.

FIG. 2 is a block diagram showing a functional configuration of theheadphone 1 including the processor 12. FIG. 3 is a flowchart showing anoperation of the processor 12. The processor 12 includes a first leveladjuster 125, a first average power calculator 126, a second averagepower calculator 127, a first storage portion 131, a second storageportion 132, a target value setter 129, a second level adjuster 151, anda third level adjuster 152. A level calculator 121 is constituted by thefirst level adjuster 125, the first average power calculator 126, andthe second average power calculator 127. The first storage portion 131and the second storage portion 132 each are constituted by the flashmemory 14.

The level calculator 121 calculates a level of the sound signal capturedby the microphone 15 during a first period. Specifically, the levelcalculator 121 calculates an average power of the sound signals capturedby the microphone 15 during the first period (S11). Note that, the levelcalculated by the level calculator 121 is not limited to an averagepower.

The first average power calculator 126 calculates an average powerduring, for example, 1000 msec as the first period. For instance, in thecase where a sampling frequency of the sound signal is 48 kHz, the firstaverage power calculator 126 calculates an average power of 48000samples containing the latest sampling data. Note that, the firstaverage power calculator 126 may calculate an average power such thatvalues of the samples each are squared, added to one another, anddivided by the number of samples, for example. Further, in calculationof the average power, frequency characteristics of the sound signal maybe corrected with an A characteristic. Thus, a power of the sound signalaffecting a hearing sense can be evaluated appropriately in theprocessor 12.

The first average power calculator 126 outputs the calculated firstaverage power to the first storage portion 131 and the target valuesetter 129. The first storage portion 131 stores the first average powerreceived from the first average power calculator 126 (S12). The firststorage portion 131 stores a plurality of first average powers. Thefirst storage portion 131 stores first average powers that arecalculated a plurality of times (e.g., four times), in which the latestfirst average power is contained.

When detecting a user's volume operation through the user I/F 17 (S13),the target value setter 129 sets a reference level (S14). Specifically,the target value setter 129 determines a target value based on thelatest first average power, which is received from the first averagepower calculator 126, and first average powers at a plurality of times(e.g., four times), which are stored in the first storage portion 131.

More specifically, the target value setter 129 further calculates anaverage of the first average powers at a plurality of times (e.g., fourtimes). The target value setter 129 sets the average of the firstaverage powers at a plurality of times (e.g., four times) as a referencelevel. Note that, when the gain specified from the user I/F 17 ischanged, the target value setter 129 sets a reference level. In otherwords, when the volume operation is received from a user, the targetvalue setter 129 calculates a reference level and performs volumecontrol using the reference level.

The target value setter 129 compares the reference level with the latestfirst average power (S15). For instance, the target value setter 129subtracts the reference level from the latest first average power. Thetarget value setter 129 sets the subtracted value as a target value(S16). If the subtracted value is a negative value, the target valuewill also be a negative value, and if the subtracted value is a positivevalue, the target value will also be a positive value. When the targetvalue is a negative value, the target value setter 129 determines thatthe present situation is in a state where the ambient environmentalsound is felt to be quieter than the reference level. Therefore, thetarget value setter 129 performs control so as to decrease the soundvolume. If the target value is a positive value, the present situationis in a state where the ambient environmental sound is felt to benoisier than the reference level. Therefore, the target value setter 129performs control so as to increase the sound volume.

However, if a difference between the past first average power and thelatest first average power is set as a target value as it is, the volumechange will be made large. Thus, a user is likely to feel sense ofincongruity. Accordingly, the target value setter 129 may reduce thetarget value by multiplying the subtracted value by a predeterminedchange ratio (e.g., ¼ to 1/12). Further, the target value setter 129 mayalso round off the target value by 0.5 dB.

Furthermore, the target value setter 129 may set a lower limit or anupper limit of the target value. For instance, the target value setter129 may set the upper limit of the target value to +3 dB, or may set thelower limit of the target value to −3 dB. Further, the target valuesetter 129 may set the upper limit of the target value to +1.5 dB, i.e.,a value smaller than the lower limit. Thus, a rising amount of volumecan be suppressed, thereby giving priority to hearing protection.

Further, the target value setter 129 may change the upper limit or thelower limit of the target value depending on a volume of the soundsignal of content. For instance, through the target value setter 129,the upper limit of the target value setter 129 is made variable between0 dB and +1.5 dB, and the lower limit of the target value is madevariable between −3 dB and 0 dB.

The first level adjuster 125 adjusts a level of the sound signal ofcontent at the same gain as that of the third level adjuster 152. Thegains of the first level adjuster 125 and the third level adjuster 152are determined depending on user's volume operation through the user I/F17.

The second average power calculator 127 calculates a second averagepower of sound signals during the first period (1000 msec). Herein, thesound signals have been subjected to level adjustment in the first leveladjuster 125. The second average power calculator 127 outputs thecalculated second average power to the second storage portion 132. Thesecond storage portion 132 stores the second average power that isreceived from the second average power calculator 127. The secondstorage portion 132 stores second average powers calculated at aplurality of times (e.g., four times), which contain the latest secondaverage power.

The target value setter 129 obtains the second average powers at aplurality of times (e.g., four times) stored in the second storageportion 132 and calculates an average thereof. The target value setter129 sets the average of the second average powers at a plurality oftimes (e.g., four times) as a regeneration level. The target valuesetter 129 subtracts the regeneration level from an upper limit (e.g.,−20 dB) of volume.

If the subtracted value is a negative value, the target value setter 129decrease the upper limit of the target value, because the regenerationlevel is too high. For instance, the subtracted value (value obtained bysubtracting the regeneration level from the upper limit of volume, i.e.,−20 dB) is added from the upper limit of the present target value.

Further, the target value setter 129 subtracts the regeneration levelfrom a lower limit (e.g., −50 dB) of volume. If the subtracted value isa positive value, the target value setter 129 increases the lower limitof the target value, because the regeneration level is too low. Forinstance, the subtracted value (value obtained by subtracting theregeneration level from the lower limit of volume, i.e., −50 dB) isadded from the lower limit of the present target value.

Next, the target value setter 129 gradually changes a gain of a secondlevel adjuster 151 to the target value over a second period (S17). Forinstance, the target value setting part 129 updates the gain graduallyat 100 msec intervals in such a manner that the gain is changed byspending 15000 msec to 20000 msec per 1 dB. For instance, if a volumedifference between the gain and the target value is 1 dB, the secondperiod will be 15000 msec. If a volume difference between the gain andthe target value is 2 dB, the second period will be 30000 msec. Byupdating the gain gradually, the target value setter 129 can reduce anamount of volume change per one time, thereby making it difficult for auser to notice the volume change. Further, the target value setter 129is not necessary to update the gain at 100 msec intervals. For instance,the target value setter 129 may gradually update the gain at 1 msecintervals or 10 msec intervals. Further, the target value setter 129 mayupdate the gain sample by sample, for example. When the gain of thesecond level adjuster 151 reaches the target value, the target valuesetter 129 stops updating the gain.

Thus, the target value setter 129 gradually changes a volume of thesound signal of content. According to the above-mentioned embodiment,the following effects are achieved.

(1) The processor 12 sets a target value based on a level (e.g., a firstaverage power during 1000 msec) of the sound signal, which is capturedby the microphone 15, during a first period. In other words, theprocessor 12 does not change a sound volume of content frequently,depending on an ambient environmental sound. Therefore, the processor 12does not give sense of incongruity, which is caused by volume change, toa user. Note that, if it takes too long to calculate the first averagepower, the sound volume will be changed too slowly. This makes itdifficult to follow a change in ambient sounds. On the other hand, if ittakes too short to calculate the first average power, the sound volumewill be changed too frequently.

This makes it easy for a user to notice the volume change. Accordingly,the period for calculating the first average power is preferably in arange from 500 msec to 5000 msec.

(2) The processor 12 changes a gain slowly and gradually over a secondperiod. For instance, the processor 12 changes the gain by approximately1/15 dB at 100 msec intervals. For instance, if a volume differencebetween the gain and the target value is 1 dB, the second period will beset to 1500 msec. If a volume difference between the gain and the targetvalue is 2 dB, the second period will be set to 3000 msec. Therefore,the processor 12 makes it difficult for a user to notice the volumechange. Note that, an interval (update interval) for changing the gainis set to a value sufficiently shorter than time required for change per1 dB. For instance, if the time required for change per 1 dB is 1500msec, the update interval will be set to 100 msec. Thus, the processor12 gradually changes the gain without causing a user to notice thevolume change. Note that, if immediate volume change is required, theprocessor 12 will not be necessary to change the gain gradually over thesecond period. For instance, the processor 12 may change the targetvalue over a period of 500 msec.

(3) The processor 12 sets a target value based on first average powers,which have been calculated in the past, and the latest first averagepower. Thus, the processor 12 slowly changes a sound volume of content,depending on a level change of ambient environmental sounds. Therefore,the processor 12 is avoided from giving sense of incongruity to a user.

(4) The processor 12 sets a reference level based on first averagepowers calculated at the time of user's volume operation. When a userperforms a volume operation, a volume balance between ambientenvironmental sounds and the sound of content is in a good state for auser. By setting the reference level based on the first average powerscalculated at the time of user's volume operation, the processor 12 canperform volume control on the basis of the state where the volumebalance is comfortable to a user.

(5) The processor 12 multiplies a difference between the past averagepower and the latest average power by a predetermined change ratio(e.g., ¼ to 1/12) to reduce the target value. Thus, the volume change issuppressed, thereby further reducing a possibility of causing user'suncomfortable feeling.

(6) The processor 12 sets a lower limit and an upper limit of the targetvalue. For instance, the processor 12 sets the upper limit and the lowerlimit of the target value to +3 dB. Thus, the processor 12 prevents auser from noticing the volume change. Further, the processor 12 may setthe upper limit of the target value to a value (e.g., +1.5 dB) smallerthan the lower limit. Thus, a rising amount of volume is suppressed,thereby giving priority to hearing protection.

Next, FIG. 4 is a block diagram showing a functional configuration of aprocessor 12 in accordance with a modification. The same referencenumerals are assigned to the same configurations as in FIG. 2, and thedescription thereof is omitted. A microphone 15 in accordance with amodification captures a composite signal in which the sound signal ofcontent, which is subjected to level adjustment in the third leveladjuster 152, is added to a sound signal in accordance with anenvironmental sound. In other words, the sound (composite signal)captured by the microphone 15 in this modification includes the sound ofcontent and an environmental sound. Herein, the sound of content is asound that is outputted from the speaker unit 16, passes through a caseof the headphone 1, a user's body (ear), a space, and the like, and isfed back. The microphone 15 outputs the composite signal to the firstaverage power calculator 126.

The first average power calculator 126 calculates an average power(third average power) of the composite signal during 1000 msec, forexample. The first storage portion 131 stores the third average power.The first storage portion 131 stores the third average powers calculateda plurality of times (e.g., four times), which contain the latest thirdaverage power.

The target value setter 129 sets a target value based on a ratio of thethird average power to the second average power. Specifically, thetarget value setter 129 divides the third average power by the secondaverage power. In the target value setter 129, the value obtained bydividing the third average power by the second average power is set asan evaluation value. The target value setter 129 subtracts a referencelevel from the evaluation value to set the target value.

In the modification, however, the reference level is calculated based ona ratio of an average of the past third average powers to an average ofthe past second average power. The target value setter 129 obtains thethird average powers at four times, which are stored in the firststorage portion 131, and the second average powers at a plurality oftimes (e.g., four times), which are stored in the second storage portion132. The target value setter 129 calculates an average of the secondaverage powers at four times and an average of the third average powersat a plurality of times (e.g., four times). The target value setter 129divides the average of the third average powers at a plurality of times(e.g., four times) by the average of the second average powers at aplurality of times (e.g., four times). The target value setter 129 setthe divided value as the reference level.

The target value setter 129 subtracts the reference level from theevaluation value to set the target value. If the subtracted value is anegative value, the target value will also be a negative value, and ifthe subtracted value is a positive value, the target value will also bea positive value. If the target value is a negative value, the targetvalue setter will perform control so as to decrease the sound volume. Ifthe target value is a positive value, the target value setter 129 willperform control so as increase the sound volume.

However, if an absolute value of the subtracted value is less than orequal to a predetermined threshold, the target value setter 129 will setthe target value to zero. When the absolute value of the subtractedvalue exceeds the predetermined threshold, the target value setter 129sets the subtracted value as the target value. Thus, an influence oferrors, which depend on a correlation component between an ambientenvironmental sound and the sound of content, can be reduced by thetarget value setter 129.

Further, the target value setter 129 may round off the target value by0.5 dB. Furthermore, the target value setter 129 may set a lower limitor an upper limit of the target value. For instance, the target valuesetter 129 may set the upper limit of the target value to +3 dB, or mayset the lower limit of the target value to −3 dB. Note that, when theabsolute value of the subtracted value exceeds the predeterminedthreshold, the target value setter 129 may set the upper limit or thelower limit as the target value.

Further, the target value setter 129 may change the upper limit or thelower limit of the target value according to a volume of the soundsignal of content. For instance, in the target value setter 129, theupper limit of the target value is made variable between 0 dB and +3 dB,and the lower limit of the target value is made variable between −3 dBand 0 dB. The manner for changing the upper limit and the lower limit,which is the same as the above-mentioned one, is based on a differencebetween an average of the second average powers at four times and anupper limit (e.g., −20 dB) or a lower limit (e.g., −50 dB) of volume.

The processor 12 in accordance with the modification sets the targetvalue based on a ratio between the sound of content and a compositesound containing the sound of content and an ambient environmentalsound. In an ear-wearing device such as a headphone, a sound outputtedfrom the speaker unit 16 is collected by the microphone 15. Thus, a loopgain is likely to occur. In this case, the target value is likely to bechanged depending on the loop gain. The loop gain, however, variesdepending on wearing conditions of a headphone. Thus, the measurementthereof is made difficult. On the other hand, the processor 12 inaccordance with the modification sets the target value based on a ratiobetween the sound of content and a composite sound containing the soundof content and an ambient environmental sound, thereby making itpossible to reduce an influence of the loop gain.

Further, in the processor 12 in accordance with the modification, thetarget value is also changed according to volume change of content. Forinstance, when the sound volume of content becomes very large, thetarget value has a negative value. As a result, control is performed soas to suppress the sound volume. Thus, the processor 12 in accordancewith the modification will perform control so as to give more priorityto hearing protection.

Note that, it is preferred that the processor 12 in accordance with themodification does not control the sound volume without setting thetarget value, until the second average power (i.e., sound volume ofcontent) becomes more than or equal to a predetermined value. Forinstance, after reproduction of content is started, a silent period isincluded for a while. Thus, the second average power (sound volume ofcontent) is lowered. It is assumed that the target value is set when thesecond average power is too low. In this case, the sound volume islikely to be increased even when a level of ambient environmental soundsis low. Accordingly, it is preferred that the processor 12 does notcontrol the sound volume without setting the target value, until thesecond average power (i.e., volume of content) becomes more than orequal to a predetermined value.

Further, in the processor 12 in accordance with the modification, it ispreferred that a period for calculating an average power is set to havea certain amount of time (e.g., 1000 msec to 5000 msec). In theprocessor 12 in accordance with the modification, the target value isalso changed depending on the sound volume of content. It is assumedthat, under a situation that the sound volume of content is changed sofrequently, if the period for calculating an average power is short, thetarget value will also be changed frequently. Therefore, in theprocessor 12 in accordance with the modification, it is preferred thatthe period for calculating an average power is set to have a certainamount of time (e.g., 1000 msec to 5000 msec).

Note that, in the above-mentioned embodiment, the processor 12calculates an average power during the first period (1000 msec) at aninterval of the first period (e.g., 1000 msec intervals). In otherwords, periods for calculating average powers are not overlapped witheach other. However, the processor 12 may calculate an average powerduring the first period (1000 msec) at an interval of the third period(e.g., 100 msec intervals) shorter than the interval of the firstperiod, for example. In this case, periods for calculating averagepowers are overlapped with each other. Thus, followability of volumechange is improved. Further, the processor 12 may calculate an averagepower during 5000 msec at 1000 msec intervals, for example.

The description of the present embodiments is illustrative in allrespects and is not to be construed restrictively. The scope of thepresent invention is indicated by the appended claims rather than by theabove-mentioned embodiments. Furthermore, the scope of the presentinvention includes the scope of the claims and a range equivalentthereto.

What is claimed is:
 1. A headphone volume control method comprising:calculating a level of a sound signal captured by a microphone during afirst period; determining a target value of a sound volume based on thelevel; setting an upper limit or a lower limit of the target value;changing a reproduction volume of content to be reproduced to the targetvalue gradually over a second period; and changing the upper limit orthe lower limit of the target value depending on a volume of thecontent.
 2. The headphone volume control method according to claim 1,further comprising: storing the level as a past value, wherein thedetermining determines the target value based on both the past value anda latest level calculated by the calculating.
 3. The headphone volumecontrol method according to claim 1, further comprising: receiving avolume operation from a user, wherein the determining determines: areference level based on the level, which is calculated by thecalculating at a time when the volume operation is received; and thetarget value based on both the reference level and the level.
 4. Theheadphone volume control method according to claim 1, wherein the soundsignal is a composite signal containing a sound signal of the contentadded to the sound signal captured by the microphone.
 5. The headphonevolume control method according to claim 4, wherein: the calculatingcalculates a level of the sound signal of the content; and thedetermining determines the target value based on a level ratio of thecomposite signal to the sound signal of the content.
 6. The headphonevolume control method according to claim 1, wherein the changing of thereproduction volume changes the reproduction volume to the target valuebased on a present reproduction volume.
 7. The headphone volume controlmethod according to claim 1, wherein the calculating calculates thelevel from an average power of the sound signal captured by themicrophone.
 8. The headphone volume control method according to claim 1,wherein: the upper limit is set to +3 dB relative to a presentreproduction volume, and the lower limit is set to −3 dB relative to thepresent reproduction volume.
 9. The headphone volume control methodaccording to claim 1, the changing of the reproduction volume changesthe reproduction volume so that time required to change per 1 dB is setto more than or equal to 1500 msec.
 10. A headphone comprising: amicrophone; and at least one processor that implements instructionsstored in a memory and executes a plurality of tasks, including: a levelcalculating task that calculates a level of a sound signal captured bythe microphone during a first period; a target value setting task thatdetermines a target value of a sound volume based on the level; a limitsetting task that sets an upper limit or a lower limit of the targetvalue; a level adjusting task that changes a reproduction volume ofcontent to be reproduced to the target value gradually over a secondperiod; and a limit changing task that changes the limit setting taskchanges the upper limit or the lower limit of the target value dependingon a volume of the content.
 11. The headphone according to claim 10,further comprising: a storage device, wherein the plurality of tasksinclude storing task that stores, in the storage device, the level as apast value, and wherein the target value setting task determines thetarget value based on both the past value and a latest level calculatedby the level calculating task.
 12. The headphone according to claim 10,further comprising: a user interface that receives a volume operationfrom a user, wherein the target value setting task determines: areference level based on the level, which is calculated by the levelcalculating task at a time when the volume operation is received; andthe target value based on both the reference level and the level. 13.The headphone according to claim 10, wherein the sound signal is acomposite signal containing a sound signal of the content added to thesound signal captured by the microphone.
 14. The headphone according toclaim 13, wherein: the level calculating task calculates a level of thesound signal of the content, and the target value setting taskdetermines the target value based on a level ratio of the compositesignal to the sound signal of the content.
 15. The headphone accordingto claim 10, wherein the target value setting task changes thereproduction volume to the target value based on a present reproductionvolume.
 16. The headphone according to claim 10, wherein the levelcalculating task calculates the level from an average power of the soundsignal captured by the microphone.
 17. The headphone according to claim10, wherein: the upper limit is set to +3 dB relative to a presentreproduction volume, and the lower limit is set to −3 dB relative to thepresent reproduction volume.
 18. The headphone according to claim 10,wherein the level adjusting task changes the reproduction volume so thattime required to change per 1 dB is set to more than or equal to 1500msec.